Deep seated gravitational slope deformations in the European Alps

• Review of deep seated gravitational slope deformation – DSGSD – at the orogen scale
• Multivariate statistical analysis of main predisposing and controlling factors on DSGSD
• Influence of shear zones, heterogeneities on stability and groundwater flow
• State of activity and influence on mountain evolution

Deep seated gravitational slope deformations (DSGSD) are widespread phenomena, recognized in different mountain ranges worldwide. The distribution of such phenomena at the scale of a mountain belt has rarely been systematically analysed in the past. Aim of the paper is to present and discuss an inventory map of DSGSD at the scale of the entire European Alps, in order to review existing knowledge and investigate general controls on these phenomena. The criteria adopted for their classification and distinction are presented. A total of 1033 DSGSDs, ranging in size between 0.03 and 108 km2, have been mapped. The inventory has been validated against available local or regional landslide inventories at different scales and prepared by different authors using different approaches. The frequency–area relationship for the mapped features is presented. The spatial distribution of the mapped DSGSD has been quantified by discretizing the study area into regular square grids with different resolution, and analysed with respect to a variety of geological, geomorpohological and morphometric variables, and of their clustering. Discriminant, principal component and cluster analyses have been performed to define the most important controlling and predisposing factors. Results suggest that the occurrence of foliated metamorphic rocks, LGM ice thickness, local relief (and related parameters), slope size, drainage density and river stream power are the local parameters most positively correlated to DSGSD occurrence. The impact of these phenomena on slope morphology, in terms of hypsometry and slope gradient adjustment is also discussed.